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Still in the process of tearing down my buddies motor. After taking the intake off I noticed a bunch of built up carbon/oil on the intake valves. His heads are fairly new maybe a year old pro comp aluminum's. Taking a look at the intake and you can see where oil is being sucked in by what im assuming is the pcv valve. PCV valve seems to working properly. I went ahead and did a cylinder leak down test. Camshaft is out already so all the valves were closed and I just rotated each cylinder to TDC. Used about 80 psi in each cylinder and all were in the teens. 12-16 at the most. All of the loss was from around the rings, but with that little (which I would consider good) loss, I wouldn't assume there is a ton of blow by around the rings? His valve covers have baffles in them. The only reason I dont think the intake gasket itself was leaking is because of the oil in the intake runners where its clearly being sucked in.

Any ideas? I know he can run a catch can, but why the need?
 

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True Hotrodder
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You probably right about the blow-by on the ring package but they are wearing out. If the bottom of the intake gasket had any leakage to the valley area, it's very easy for it to pull oil into the intake runners.
 

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Race it, Don't rice it!
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ProComp is known for having crappy valve guides and guide life and if you add the wrong push rod lenght then the wear is accelerated. This may not show up on a leakdown if the valves are closed with a good seal. Sometimes if it's bad enough, you can whack the valve with a rubber hammer to snap it open a few times. Each time it closes the valve sits on the seat in a slightly different place and you get leakage. Left this way, eventually the head will break off. Valve guides and fitment are important.
Oil in the intake could be a symptom of reversion into the intake or generally improper camshaft and tuning.
 

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When it comes to rings there are two principle failure modes that of the compression rings which leads to blow by and that of oil control rings which leads to oil pumping into the combustion chamber leading to smoke in the exhaust. You can get one, the other, or both depending on the cause of the problem being rings themselves or piston fit wear to the cylinder wall.

Coked oil on the back of intake valves is usually oil getting down the guides but can also be a vacuum leak on the valley side of the intake gasket. For the most part oil down the guides boils down to leaking seals or excessive guide to stem clearance which makes it impossible for the seal to do its function. This is way higher on my list of candidates than pulling oil over the PCV. The intake side is subject to manifold vacuum so it is harder to seal up than the exhaust guides.

These aftermarket heads suffer a lot from this problem in my experience the two or three major causes are insufficient cleaning of the guides, insufficient initial lubrication in the guides, improper rocker contact on the stem combined with high spring force. You need to pull the heads and check the guides and stems for wear and recheck the pushrod length to insure proper addressing of the rocker to the stem. A reason why GM usually uses an iron guide in production heads as they are less fussy about lubrication and cleanliness, plus wear better than bronzes do.

I would consider your 12% leak down as heading toward the high end of the scale for a pretty fresh engine.

Bogie
 
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